1. Field of the Invention
The present invention relates to a method for reducing reactive shale and/or clay swelling in under-balanced drilling operations and to methods for making and using same.
More particularly, the present invention relates to a method for reducing reactive shale and/or clay swelling in under-balanced drilling operations using a drilling fluid including an anti-swelling additive having an effective amount of a choline salt (a 2-hydroxyethyl trimethylammonium salt), an under-balanced, drilling fluid including an effective amount of choline salt and to methods for making and using same. The present invention also relates to general purpose drilling fluids for overbalanced drilling, fracturing fluids, and completion fluids including an anti-swelling additive having an effective amount of a choline carboxylate salts and to methods for using same.
2. Description of the Related Art
Shale and/or clay swelling is a common problem during the drilling phase. This problem leads to potential stuck-pipe or lost circulation both of which can increase drilling costs and/or impede production rates. This is especially true when the composition or continuous phase of the drilling fluid is comprised of water. Water in the form of mist, steam or foam is one of the main components of an under-balanced drilling fluid; as a result, shale and/or clay-stabilizing technology is a critical when using an under-balanced drilling fluid.
Historically, shale and/or clay-stabilizing technology has consisted primarily of potassium chloride, potassium formate and anionic polymers/co-polymers.
U.S. Pat. No. 5,635,458 teaches the use of a conventional drilling fluid that reduces water adsorption and hydration of argillaceous rocks. This conventional drilling fluid includes a glycol having a molecular weight of less than about 200 a concentration of at least 10% by weight of the aqueous phase of said drilling fluid, an organic cationic material such as salts of choline or an organic salt of potassium, a filtration control agent, a viscosifier and water.
U.S. Pat. No. 5,908,814 teaches the use of drilling fluid additives that suppress clay selling within a subterranean well and to methods for controlling clay selling during the conventional drilling of a subterranean well. This conventional drilling fluid is comprised of a weight material (barite, hematite, iron oxide, calcium carbonate, magnesium carbonate, and combination thereof), an anionic polymer, and a reaction product of a tertiary amine and an compound having the formula R—X, where R is an alkyl group having up to four carbon atoms, and X is a halogen selected from the group consisting of chlorine, bromine, iodine, or combinations thereof. The tertiary amine has the formula NR1R2R3 where R1 and R2 are methyl or hydroxyalkyl groups with one to three carbon atoms, or combinations thereof, and R3 is a hydroxyalkyl group with one to three carbon atoms.
U.S. Pat. No. 6,247,543 teaches the use of a conventional drilling fluid for use in drilling wells through a formation containing a shale, which swells in the presence of water, where the drilling fluid includes an aqueous based continuous phase, a weight material, and a shale hydration inhibition agent having the formula: H2N—CH(CH3)CH2[—OHCH2CH(CH3)—]x—NH2 a shale hydration inhibition agent, where the shale hydration inhibition agent is present in sufficient concentration to reduce the swelling of the shale.
Although drilling fluids have been developed with shale hydration inhibitors, there is still a need in the art for drilling fluids, especially drilling fluids for under-balanced drilling, that reduce the swelling tendency of reactive shale and/or clay.